Patient procedures chairs designed for otolaryngologists, plastic surgeons, dermatologists, oral maxillofacial surgeons and other specialists who require maximum access to the head and neck areas of patients are typically provided with mechanism for positioning the chair's headrest at selected positions relative to the back section of the chair. In a somewhat different aspect it is conventional to provide side rails on such chairs and other patient tables to support various accessories. It is desirable, in this context, to be able to position the rails outwardly of the sides of the chair or table, or inwardly along their sides to allow the physicians to have better access to their patients. In either case, the mechanism for positioning the headrests or rails is often cumbersome and inconvenient to operate.